1. Technical Field
The present invention relates to: a communication system achieving communication between a vehicle such as an electric car and hybrid car and an electricity supply apparatus supplying electricity to the vehicle; and a communication device constituting this communication system.
2. Description of Related Art
In recent years, as techniques used for treating global warming, attention is focused on environmental technology. As such environmental technology, for example, electric cars, hybrid cars, and the like in which a secondary battery is mounted and an electric motor is employed as a drive unit in place of a conventional combustion engine that consumes gasoline have been brought into practical use.
Such a vehicle like an electric car and a hybrid car has a configuration that a charging plug connected to an external electricity supply apparatus is connected to the connector of a power feed opening provided in the vehicle so that the secondary battery is allowed to be charged from the outside of the vehicle.
An interface used between a vehicle and an electricity supply apparatus (a charging station) when electricity is to be supplied to the vehicle has already been standardized. For example, a signal line called a control pilot line is provided between an output circuit provided on the electricity supply apparatus side and an input circuit provided on the vehicle side. Then, a rectangular wave signal (a control pilot signal) of given frequency is outputted from the output circuit to the input circuit so that information such as the charging state of the vehicle is allowed to be checked between the electricity supply apparatus and the vehicle (see “SURFACE VEHICLE RECOMMENDED PRACTICE, SAE International (Society of Automotive Engineers International), January 2010.”.
On the other hand, a communication system is also investigated in which a communication signal is superimposed on the control pilot line so that various kinds of further information is allowed to be transmitted and received between the electricity supply apparatus and the vehicle.